Answer:
Two equal and opposite parallel forces not acting along the same line, form a couple. A couple is always needed to produce the rotation.
For example, turning a key in a lock and turning a steering wheel.
Q=mcΔt
Q= 1kg * 800J/kg°C*4°C
Q= 3200J
Answer:
The mass percentage of calcium nitrate is 31.23%.
Explanation:
Let the the mass of calcium nitrate be x and mass of potassium chloride be y.
Total mass of mixture = 19.12 g
x + y = 19.12 g..(1)
Mass of solvent = 149 g = 0.149 kg
Freezing point of the solution,
= -5.77 °C
Molal freezing constant of water = 1.86 °C/m =1.86 °C/(mol/kg)
The van't Hoff factor contribution by calcium nitrate is 3 and by potassium chloride is 2.So:
i = 3
i' = 2
Freezing point of water = T = 0°C




On solving we get:
....(2)
Solving equation (1)(2) for x and y:
x =5.973 g
y = 13.147 g
Mass percent of
in the mixture:

The mass percentage of calcium nitrate is 31.23%.
Answer:
Option D is correct: 170 µW/m²
Explanation:
Given that,
Frequency f = 800kHz
Distance d = 2.7km = 2700m
Electric field Eo = 0.36V/m
Intensity of radio signal
The intensity of radial signal is given as
I = c•εo•Eo²/2
Where c is speed of light
c = 3×10^8m/s
εo = 8.85 × 10^-12 C²/Nm²
I = 3×10^8 × 8.85×10^-12 × 0.36²/2
I = 1.72 × 10^-4W/m²
I = 172 × 10^-6 W/m²
I = 172 µW/m²
Then, the intensity of the radio wave at that point is approximately 170 µW/m²
If you move a magnet through a loop of wire, induction will happen. The more loops you make, the stronger the effect becomes.